Chapter 4
Obesity
Kate, 20, 5 ”7’ 160lbs, regular walker/ lifts weights, at physical “borderline obese” according to height and weight chart but…..feels good?
Questions
What does it mean to be overweight?
What does it mean to be obese?
What is the relationship b/w overweight and obesity?
What % body fat determines obesity?
How would exercise prescriptions differ for the obese?
What are the primary factors contributing to body fat?
Can you lose BF in selected areas w/ specific exercises?
Assumptions
* There are essential fat levels
* Obesity/overweight are related but not interchangeable
* A person can be overweight w/out being obese
* Obesity is a health hazard of epidemic proportions in
most developed developed countries
I.Distinguishing b/w overweight/obesity
A.Terms
- Overweight: weight exceeds (+ 20%) an arbitrary figure based on height/ frame.
2. Obese: an “overfat” level that is associated
with increased risks of serious and sometimes
fatal diseases
B.Types and Trends of Obesity
“TYPES” (overhead): what obesity looks like
- Android/apple: (m) much more fat on the upper body than the lower body
* associated w/ higher risk of CVD
- Gynoid/pear: (w) fat is much greater below the waist
“TREND” How obesity typically occurs
- Creeping obesity: gradual and consistent weight gain over the yrs (+ energy balance)
* most people gain 1.5lbs of fat per year and
lose about 1 lb of muscle per year….
* as you age your metabolic rate decreases.
What typically happens to your caloric intake?
* Currently approx 55% of Americans are
overweight and 22% are obese
2. Obese kids
* obesity among kids has increased dramatically; especially the superobese!
C. Body Fat Ranges
TypeMF
Essential Fat3%12%
At risk 5% 8%
Desirable (good P) 6-14% 9-22%
Average15%23%
Desirable (good health)10-25% 18-29%
Overfat/Obese 25% 30%
1. Essential Fat: minimal amt of fat needed for
physiologic f(x).
*These fats are incorporated into the nerves,
brain, heart, lungs, liver, mammary glands etc..
cells, organs..
* Provide insulation, stored energy, and promote
normal bodily f(x)
* too little fat affects the hormonal balance in
W; can cause excessive bone/muscle loss,
a variety of physiological problems (overhead)
* EF is higher in women due to deposits in the
breasts, uterus, and other specific sites
* Nonessential fat exists primarily within the fat
cells (adipose tissue), often located just below the skin and around major organs.
2. Desirable Performance/Fitness
* athletes, fitness buffs etc
3. Desirable Good Health
* Healthy People 2010
* Physical Activity/Exercise Guidelines
4. Obese
* Men: above 25% body fat =obese
* Women: above 30% body fat =obese
* obese levels of body fat increase the risk of
contracting diseases that impair the quality of life and are often fatal.
* a persons body fat is a much truer measure of
relative health than is body weight
II. Factors affecting body fat/weight control
A.Genetics: about 25% of body fat is related to genetics.
* Influence body size + shape, distribution of
fat, metabolic rates, and propensity for weight
* Studies show that if both parents are
overweight, their children are 2x as likely to
be overweight as kids than if just one parent is
overweight
* Heredity influences must be balanced against
environmental factors like diet and exercise.
Genes exert significant influence but they are
not destiny.
B.Energy Balance and Metabolism
Energy balance is affected by CI, genetics,
Lifestyle choices, and metabolic rates,
Positive energy balance: consume more cals than you expend = weight gain;
+ energy balance: CI > CE = weight gain
* Most people who are overweight don’t
suffer from thyroid problems..rather
they’ve developed long-term (+)
energy balance
Negative energy balance expend more cals than you take in = weight loss
- energy balance: CI < CE = weight loss
Metabolism: the sum of all the vital processes by which food energy and nutrients are made available to and used by the body
Basal Metabolic Rate: The metabolic rate necessary to sustain life.
* infl by gender (M higher), age, body size
(larger bodies, higher), metabolic functions
(thyroid), body characteristics; varies
* Body comp: affects BMR; lean tissue requires
energy=incr BMR; Fat is metabolically inert;
Resting Metabolic Rate: Calories exerted beyond just “being alive”; as well as those calories necessary to sustain life.
* accounts for 55-75% of CE
* The energy required to maintain vital body
functions, including respiration, HR, body temp (thermogenesis), and BP, while the body is at rest; A typical inactive day.
* A typical RMR is @1500 cals…..
* RMR is dictated by many factors, including
genes and behavior. Exercise has a + effect on metabolism. RMR Drops as you age
* The body defends its original weight by
decreasing RMR when weight is lost…
* digestion accounts for 5-15% of daily CE
C.Lifestyle choices: Physical Activity:
* accounts for 10-40% of daily CE….right?
* Lifestyle: many Americans choose sedentary
lifestyles/occupations… typical lifestyle for
college students?
* most obese people don’t exercise or are unable
to do so. Those who do tend to lose weight.
* consider CI in relation to lifestyle
* “Take in more calories than you expend, and
gain weight. Expend more calories than you
take in, lose weight”
D.Psychological, social, and cultural factors
* Many people use food as a way of coping with
stress and distracting them from difficult or
negative emotions. Why not use exercise?
* Obesity is strongly associated w/ SES
prevalence of Ob goes down as SES rises
* In some families and cultures, food is used as a
symbol of love and caring (examples?)
III.Categories of problems associated w/ obesity
Epidemiological: the study of the distribution of diseases in populations, their causes, and the ways in which they can be prevented and controlled.
* obesity causes or is associated w/ many health
problems ranging from CVD, Diabetes,
Hypertension, and some cancers
* People w/ excessive body fat who have diabetes or CV risks benefit (lower bp and total
chol) from even modest (5-10%) weight loss
Mental Health: obesity is also associated w/ higher levels of anx/dep; lower levels of self esteem
Socioeconomic: obesity is associated with lower income and career advancement
Social: Obesity is associated with lower likelihood of marriage
Mortality Rates: all cause mortality rate is 2x’s as high in the obese
* People who are slightly overweight but otherwise
are healthy/active/eat a good diet may not be at
greater risk for early death.
Metabolic Profile: As BW incr so does bl chol + triglycerides.
* these health risks can be reversed by losing weight (lowers cholesterol)
IV.Assessing Body Composition
Body Composition: “what are bodies are made of”
* The percentage of lean tissue (muscle/bone) vs Fat tissue (subcontaneous and essential fat)
A better measure than:
* Height/weight charts: (doctors office)
* Body types: ectomorphic (slender/ angular),
mesomorphic (husky/muscular), endomorphic
(plump/fat)
A.Lab methods to determine body comp
- Hydrostatic weighing (underwater):
* Measuring body density and converting that to percentage body fat
* Body density = body’s weight/body volume
* Body Volume = scale weight – weight under water
* Fat is less dense than muscle. Thus overweight indivs weigh less in water = greater body volume
* gold standard, most effective, most $,
other techniques are correlated against it
* can take up to 30 minutes; lab
- Bioelectrical impedance:
* correlates @ .9 to .94 w/ Hydrostatic estimates
* 4 electrodes are attached at the ankle, foot, wrist, and back of hand.
* Current is passed through distal electrodes (foot and hand). Proximal electrodes (ankle and wrist receive current.
* conduction through tissue depends on water & electrolyte distribution.
* FFM contains almost all the body water and conduction electrolytes.
B.Field methods to determine body comp
3. Body Mass Index (BMI):
incorporates height and weight to establish critical fat values
* Body Weight /Body height = BMI
* lower BMI the less risk
* used to screen groups (developed from insurance company mortality statistics)
4. Skinfold measures: quantify subcutaneous fat at various sites on the body.
* MOE +/- 3-4%;
* correlates 9 to .96 w/ HW with a trained tech
* m: chest, abdomen, thigh
* w: triceps, sprailium, thigh
* Why are there different sites for men/women?
* Trained, same time of day, right side of body
5. Circumference measurements:
* waist/hips circumference ratio
* Higher the ratio the higher the CV risk
* For men < 1 in “safe range”
* For women < .8 in “safe range”
* Explain the difference in terms of “types”
* best with people who appear obese b/c its difficult to get accurate skinfold
V.Desirable weight range
* A body composition within the good performance or good health range. No ideal weight per se
* Is Kate, 20, 5 ”7’ 160lbs, 25 % BF too heavy?
* Kate decides that though she is in the “healthy” range, 20% body fat may be better for her. How much weight does she need to lose?
1. Determine her FAT WEIGHT
* 160lbs x .25= 40lbs
2. Determine her FAT FREE WEIGHT
* 160lbs – 40lbs= 120lbs
3. Determine her GOAL FOR FAT FREE MASS
* 100% - 20% = 80% fat-free mass
4. Apply her GOAL FOR FAT FREE MASS
* 120lbs divided by .8 = @150
5. Determine her FAT LOSS GOAL
* 160 lbs – 150lbs = 10lbs of fat
A.Losing weight
* Approximately: a negative energy balance of
3500 cals to lose 1 lb
* a safe weight loss goal is 1-2lbs per week. How long would can Kate plan to safely lose her weight?
* 500-1000 less cals a day= 3500-7000 cals per week.
* If Kate wants to lose 10lbs=@35000 cals
* she could expect to change her body comp
in 5-10 weeks